Work feed mechanisms for sewing machines

ABSTRACT

In a work feed mechanism for a sewing machine in which a feed dog is pivotally supported by a bidirectional joint on one end of a feed bar which is oscillated by feed and lift cams to determine work feed and return strokes of the feed dog, means for constraining the feed dog so that the work fabric is transported in a straight line transversely of the work supporting surface. This constraining means comprises a block secured to the machine frame which has a throat into which is received a guide pin secured to a feed dog carrier so that the guide pin is under the control of the constraining block to maintain the feed dog parallel to the work support surface and parallel to the direction of the work feed although swinging in an arcuate or elliptical path in response to movement of the feed bar.

[ Nov. 25, 1975 United States Patent [1 1 Daman et al.

Primary ExaminerH. Hampton Hunter WORK FEED MECHANISMS FOR SEWING MACHINES Attorney, Agent, or Firm-Robert E. Smith; Marshall .I. Breen; Edward L. Bell [75] Inventors: Louis E. Daman, Martinsville;

Stanley J. Ketterer, Jamesburg, both of NJ.

[73] Assignee: The Singer Company, New York,

which a feed dog is pivotally supported by a bidirectional joint on one end of a feed bar which is oscillated by feed and lift cams to determine work feed and [22] Filed: Mar. 20, 1975 A l N 560,413 return strokes of the feed dog, means for constraining the feed dog so that the work fabric is transported in straight line transversely of the work supporting sur- 112/215 face. This constraining means comprises a block se- D05]; 27/02 cured to the machine frame which has a throat into [58] Field of Search............................. 112/215, 203

A 0 5L Um UH UH which is received a guide pin secured to a feed dog carrier so that the guide pin is under the control of the [56] References Cited UNITED STATES PATENTS constraining block to maintain the feed dog parallel to the work support surface and parallel to the direction .of the work feed although swinging in an arcuate or elliptical path in response to movement of the feed bar.

112/215 Szostak....... 112/215 6 Claims, 5 Drawing Figures U..S.. Patent Nov. 25, 1975 WORK FEED MECHANISMS FOR SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to sewing machine work feeding mechanisms, particularly of the drop feed or fourmotion variety, in which a work-engaging feed dog is raised into work engagement during a feed advance stroke, and drops out of work engagement during a return stroke.

This invention particularly concerns a new and improved means for maintaining the feed dog always parallel to the line of feed in order to provide for the transportation of the work fabric in a straight line from the stitching point.

A prior mechanism for maintaining the feed dog always parallel to the line of feed is the work feed mechanism described and claimed in the US. Pat. No. 3,527,183, which issued Sept. 8, 1970 and which utilizes an anchor link which cooperates with an elongated feed bar to which the feed dog was connected adjacent the stitching point. By the use of actuating linkages, the feed bar was oscillated in one direction to provide for feed advance and return motion, and in a perpendicular direction to provide for raising and falling motion of the feed dog. However, inasmuch as the feed dog was anchored to the feed bar, which, in turn, was supported in the sewing machine frame in gimbals, located at the extremity opposite the feed dog, it was necessary to provide the work feed mechanism with an anchor link to constrain the feed dog so that, although swinging in an arcuate path during the work feed strokes, it would always be maintained parallel to the direction of work feed.

SUMMARY OF THE INVENTION This invention eliminates the anchor link without eliminating the function accomplished by the link and thus simplifies the work feed mechanism of a sewing machine by the provision of a constraining mechanism secured to the machine bed which receives a guide pin in a throat which is parallel to the line of feed of the feed dog so that the guide pin, and thus the feed dog carrier, as it is moved by the feed bar to which the feed dog carrier is secured, is constrained to move a work fabric in a straight line transversely of the work-supporting surface as the feed bar oscillates the feed dog carrier in an elliptical path in the feed lift and the feed advance cycles.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings of the preferred embodiment:

FIG. 1 is a perspective view of a work feed mechanism of this invention removed from the sewing machine frame and with only a portion of the sewing machine bed shaft illustrated therewith;

FIG. 2 is an exploded enlarged perspective view of a fragment of the feed bar showing the bidirectional joint connection thereof to the feed dog carrier;

FIG. 3 is an elevational schematic illustration, somewhat exaggerated to show the action of the constraining element on the feed dog as moved by the feed bar; and

FIG. 4 is a plan view similar to FIG. 3, and

FIG. 5 is a representation of the path of motion of the feed dog during a typical work feeding cycle.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIGS. 1 and 2 where the work feed mechanism 10, of the drop feed variety, is shown apart from a sewing machine frame but is shown to include a bed shaft 12 which is adapted to be driven by a set of beveled gears, one of which is shown at 14,

which is ultimately connected. to the actuating mechanism of the sewing machine. The bed shaft 12 is rotated in synchronism with the actuating mechanism of the sewing machine by suitable gearing so as to move a feed dog 16 to effect transport of work fabric across a work-supporting surface of the sewing machine. As hereinbefore mentioned, the work feed mechanism 10 provides not only motion to the feed dog in the line of feed, but it elevates the feed dog up through a throat plate (not shown) during the work feeding stroke and drops the feed dog beneath the level of the throat plate during the return stroke of the feed dog.

As shown in FIGS. 1 and 2, the feed dog 16 is secured by screws 18 to a top horizontally disposed flange 20 of a feed dog carrier 22. The vertical portion or leg 24 depending from flange 20 is connected to a yoke 26 by means of a threaded screw 28 with a shoulder 30. The threaded screw fits into a threaded bore 32 in the yoke 26, while the shoulder 30 is received in a bore 34 in the vertical portion 24 of the carrier. This permits vertical pivotal motion between the carrier 22 and the yoke 26. The yoke is, in turn, connected to a collar 36 on one end of a feed bar 38 by means of a trunion pin 40 which is held in place by set screw 42. Thus connected, there is a bidirectional joint formed between the feed dog carrier 22 and the feed bar 38.

The feed bar 38 extends lengthwise of the sewing machine bed and at the extremity opposite the collar 36, the feed bar is supported in a gimbal indicated in its entirety as 44. For a more detailed explanation of the various elements of the gimbal, including the manner of supporting the same in the sewing machine frame, reference is made to the aforementioned US. Pat. No. 3,527,183.

Between its extremities, the feed bar 38 is formed with a block 46 extending transversely thereof. Freely journalled in a bore 48 in the block 46 is a pin 50 through which all motion is imparted to the feed dog 16.

The bed shaft 12 which, as previously described, is driven in synchronism with the actuating mechanism of the sewing machine, is provided with a feed advance eccentric 52 and feed lift cam .54 for imparting motions to the feed dog.

To provide the lift at the beginning of the work feed stroke and drop of the feed dog at the return stroke, the feed lift cam 54 is connected to a bifurcated extremity of a lever 56 fulcrumed on a stud 58 carried in the sewing machine bed. Lever 56 is pivotally connected to a lever 60 which, in turn, is connected to the aforementioned pin 50 in the block 46. Rotation of the bed shaft 12 thus imparts the lift and drop stroke to the feed dog 16.

To provide the work feed and return stroke of the feed dog, the feed advance eccentric 52 is connected to a link 62 through a pitman 64 and link 62 is, in turn, connected to the pin 50 on the side of the block 46 opposite from the lever 60. A pivot pin 66 provides a movable pivotal connection or toggle between the link 62 and the pitman 64 which is oscillated in response to rotation of the feed advance eccentric 52. The oscillation of this toggle connection is controlled by a slide block 68 journalled on the pivot pin 66 and constrained in a guide slot 70 formed in a feed block 72; the latter being connected to a rock shaft 74 journalled in the sewing machine bed. The angular position of the rock shaft 74 dictates the feed advance movement imparted to the feed dogs through the pin 50 by controlling the oscillatory movement of the slide block 68, thus determining the stitch length and direction of work feed. The position of the rock shaft 74 is controlled by control members, such as control arm 76 and control link 78, the function of which is more fully disclosed in the aforesaid US. Pat. No. 3,527,183.

Again, for more details of the operation of the mechanisms which are connected to the feed advance eccentric and the feed lift cam, such as, for example, the fine adjustment of the height to which the feed dog will be elevated during the lift stroke and the means for compensating for the motion of the feed bar without causing binding in the linkages, reference is also made to the aforesaid U.S. Pat. No. 3,527,183.

The motion which is imparted to the feed dog 16 by the feed bar 38 in'response to the feed lift and feed advance mechanisms just previously described, occurs in an arcuate path about the mutually perpendicular axes defined by the gimbal 40. It has been found that if the feed dog is permitted freedom to pivot without constraint, work fabric will be transported in a curved path across the sewing machine work supporting surface bed, which path will have a radius of curvature substantially equal to the length of the feed bar. In order to adapt this feed mechanism for transporting work fabrics in a straight line transversely across the work supporting surface, the movement of the feed dog is constrained to maintain the rows of feed dog teeth always parallel to the same line. Such constraint of the feed dog is accomplished by means of a constraining mechanism 80.

Constraining mechanism 80 comprises a constraining block 82 which is affixed to the sewing machine frame by any suitable means; oblong holes 84 being shown to receive suitable fastening screws yet allow a certain amount of adjustment of the block relative to the feed dog carrier and the machine frame. The block 80 is provided with a cylindrically walled bore 86 to receive a liner 88 having a cylindrical outer wall to conform to the cylindrical walled bore. The block 82 has a groove 90 which opens into the bore 86 and the liner 88, too, has an upwardly extending groove 92, having parallel substantial straight sidewalls which groove 92, together with the groove 90, form an open upwardly extending throat to receive a guide pin 94. The liner is maintained in the bore by a set screw 96 which, together with a head 98 on the liner, serve to position the liner in the block. By means of the set screw 96, the liner 88 may be secured in the bore 86 with the straight sides of the groove 92 arranged at any desired angle and this angle can be readily adjusted to provide for the desired constraint of the feed dog. The guide pin 94 is received in an aperture 100 in the vertical portion 24 of the feed dog carrier 22, and is constrained in the throat of the constraining block although allowed to move in response to actuation of the feed bar.

Again, as previously described, the motion imparted to the feed dog 16 by the feed bar 38 is a four-motion cycle, which motion defines an elipse as shown in FIG. transversely of the work supporting surface and one purpose of the guide pin is to constrain the feed dog limbs always parallel to the same line. This is accomplished by engagement of the guide pin within the throat of the constraining block fixed to the sewing machine bed so that the feed dog moves in a straight line without turning about the pin 40 during the work advance motion.

FIGS. 3 and 4 are exaggerated schematic illustrations to show the effect of the constraining element on the feed dog. The exaggeration of FIGS. 3 and 4 can be appreciated by the fact that the work feed stroke may vary only a small increment, i.e., less than one-sixteenth to one-fourth inch to a feed bar length of about 7 inches.

FIGS. 3 and 4, moreover, should be considered with regard to FIG. 5 which illustrates the eliptical path of motion of the feed dog during one typical cycle of motion.

In FIGS. 3 and 4 the feed dog is shown in solid lines in the position it occupies midway of its work feeding stroke. This position is indicated at A in FIG. 5 i.e. the feed dog is at its highest lifted position and is at the halfway point in its work advancing stroke.

In FIG. 3, the front elevational view, the dotted line illustration shows the feed dog in the position it occupies midway of its return stroke. This position is indicated at B in FIG. 5, i.e., the feed dog is at its lowest position and is at the halfway point in the return stroke.

In FIG. 4, the top plan view, the feed dog is shown in solid lines in the same position within a cycle as is illustrated in solid lines in FIG. 3 but the dotted line illustration shows the feed dog in the position it occupies at the beginning of a feed stroke. This position is indicated at C in FIG. 5; i.e., the feed dog is in its most forward position and is approximately midway between its lowest and highest elevations.

It will be apparent from FIG. 4 that the straight guide pin 94 movable axially in the groove 92 will maintain the feed dog limbs constantly parallel to a predetermined line parallel to the groove 92.

FIG. 3, however, illustrates that the groove 92 if set at an appropriate angle 0, can eliminate tipping of the feed dog; i.e. keeping the feed dog limb parallel, for instance, to the conventional throat plate through which such feed dogs are usually operative.

It is pointed out that the angular adjustment 0 of the groove 92 in the constraining member 88, although it is slight, is none-the-less critical and important to even straight work transport by the present feed mechanism. Moreover, the angular adjustment 0 should preferably take account, not only of the lateral component X of feed dog movement occasioned by the feed lift as illustrated in FIG. 3, but should also take corrective account of the slight lateral component Y of feed dog movement shown in FIG. 4 and occasioned by the arcuate path of feed advance movement imparted by the swinging feed bar 38.

What is claimed is:

1. A work feeding mechanism for a sewing machine having a work supporting surface on the bed of the machine for feeding said work fabric transversely across said work supporting surface, said work feeding mechanism comprising:

an elongated feed bar arrangedin said bed and extending substantially perpendicular to the work feed direction,

a feed dog arranged to engage said work and transport the same on said work supporting surface,

means beneath said work supporting surface pivotally securing said feed dog to one extremity of said feed bar,

gimbal means mounted in said bed and engaging the opposite extremity of said feed bar,

drive means operable in timed relation with said sewing machine for oscillating said feed bar about said gimbal means in mutually perpendicular directions, one direction being transversely of said work supporting surface to provide the work feed and return strokes of said feed dog and the other direction being toward and away from said work supporting surface to'raise said feed dog to a position above said work supporting surface during the work feed stroke and to drop said feed dog below said work supporting surface during the return stroke,

constraining means located below said means pivotally securing said feed dog to said feed bar and affixed to said machine bed for maintaining said feed dog substantially straight with respect to the work supporting surface so the said feed dog remains .means to said carrier comprises a guide means received in said throat means and affixed. to said carrier.

5. The work feed mechanism as claimed in claim 4 wherein said guide means comprises a guide pin.

6. The work feeding mechanism as claimed in claim 5 wherein said constraining block further includes a liner forming part of said throat means and providing a means for adjusting said throat means with respect to said guide pin. 

1. A work feeding mechanism for a sewing machine having a work supporting surface on the bed of the machine for feeding said work fabric transversely across said work supporting surface, said work feeding mechanism comprising: an elongated feed bar arranged in said bed and extending substantially perpendicular to the work feed direction, a feed dog arranged to engage said work and transport the same on said work supporting surface, means beneath said work supporting surface pivotally securing said feed dog to one extremity of said feed bar, gimbal means mounted in said bed and engaging the opposite extremity of said feed bar, drive means operable in timed relation with said sewing machine for oscillating said feed bar about said gimbal means in mutually perpendicular directions, one direction being transversely of said work supporting surface to provide the work feed and return strokes of said feed dog and the other direction being toward and away from said work supporting surface to raise said feed dog to a position above said work supporting surface during the work feed stroke and to drop said feed dog below said work supporting surface during the return stroke, constraining means located below said means pivotally securing said feed dog to said feed bar and affixed to said machine bed for maintaining said feed dog substantially straight with respect to the work supporting surface so the said feed dog remains parallel to the work supporting surface and the work fabric is fed on a substantially straight line.
 2. The work feed mechanism as claimed in claim 1 further including a carrier supporting said feed dog and wherein said constraining means includes means connecting sAid constraining means to said carrier.
 3. The work feed mechanism as claimed in claim 2 wherein said constraining means comprises a constraining block with a throat means opening upwardly toward said feed dog.
 4. The work feed mechanism as claimed in claim 3 wherein said means connecting said constraining means to said carrier comprises a guide means received in said throat means and affixed to said carrier.
 5. The work feed mechanism as claimed in claim 4 wherein said guide means comprises a guide pin.
 6. The work feeding mechanism as claimed in claim 5 wherein said constraining block further includes a liner forming part of said throat means and providing a means for adjusting said throat means with respect to said guide pin. 